Low Protein Expression of MET in ER-positive and HER2-positive Breast Cancer

Aim: The mesenchymal epithelial transition factor (MET) is a receptor tyrosine kinase that plays a key role in cell survival, growth, angiogenesis and metastasis. Because its expression is frequently altered in tumors, MET is currently under investigation as a potential target for anticancer therapy. The purpose of the present study was to determine the prognostic value of tumor MET expression levels in patients with estrogen receptor (ER)-positive and human epidermal growth factor receptor 2 (HER2)-positive breast cancer, in order to strengthen the rationale for targeted therapy using MET inhibitors in this breast cancer subpopulation. Materials and Methods: We determined the expression of MET in formalin-fixed paraffin-embedded surgical specimens of ER- and HER2-positive breast cancer by immunohistochemistry. Results: Comparisons of MET expression with clinical parameters, including survival of the patients, were performed with MET expression as a dichotomized variable classified as high or low. Out of 78 tumors, 3 (3.8%) showed high MET expression. The analysis examining the association between MET and survival did not yield any statistically significant result regarding overall survival or disease-free survival. Conclusion: ER- and HER2-positive breast carcinomas do not exhibit high MET expression. This null finding, the first to be reported in the literature, is of great importance, since it indicates that this sub-group population is not proper candidate for clinical trials with MET inhibitors.